How can the user know that he can enter list of emails separated by commas?

1. How do I add a comma between email addresses in Excel?
2. How do I separate BCC emails in Outlook?

How do I add a comma between email addresses in Excel?

In the Add Text dialog box, type the comma sign into the Text box, then select the After last character in the Position section, and finally click the OK button. The comma now is added after each cell text in selected range.

How do I separate BCC emails in Outlook?

Microsoft Outlook uses the semicolon as a separator between addresses. However, a natural way to type multiple addresses into the To, Cc, or Bcc fields is to use commas.